1. Technical Field
This disclosure relates generally to laser machining and, more particularly, to controlling and removing byproducts of laser ablation to ensure a consistent ablating process and to maintain proper industrial hygiene.
2. Background Information
An aircraft propulsion system may include components that are constructed from structural acoustic panels. As is known to those skilled in this art, a typical acoustic panel includes a face sheet and a back sheet and at least one layer of core, such as a honeycomb core, in between the face sheet and back sheet. The face sheet is perforated. The core, the face sheet, and back sheet together define many small acoustic chambers that are open to the air outside of the face sheet via the perforations. The chambers act to damp acoustic noise by generating an out of phase sound wave that destructively interferes with sound waves hitting the panel.
In modern aircraft, an acoustic panel is frequently constructed from a face sheet and a back sheet made of a composite system such as carbon fiber reinforced epoxy, and from a honeycomb core made from aluminum But, of course, a variety of other materials are possible and may be selected in order to suit a particular application.
One challenge in the construction of acoustic panels is the perforation of the many small holes in the face sheet. Often the holes are on the order of 0.050 inches in diameter down to much smaller diameters, and 10-30% of the face sheet area is removed by the perforation. This means that in some components millions of holes must be formed, and this must be done in an economical and consistent, reliable fashion.
Perforation using a laser beam has been proposed, and is a very attractive option. However, a method and means are needed in order to collect the byproducts of the laser ablation process, especially when conducted on composite materials like carbon fiber reinforced epoxy. The laser beam may be sensitive to being refracted by the small byproduct particles generated during ablation. These particles need to be removed from between the laser's lens and the work piece to ensure a consistent ablation process. Also, the byproducts need to be properly removed to maintain appropriate industrial hygiene.